This invention relates to light switches for use in optical fiber communication systems and more particularly to those of the type capable of light-path switching between a multitude of optical fibers.
Recent improvements in the quality and performance of semiconductor devices, optical fibers and other devices for communication use are remarkable and light transmission systems employing such devices are being vigorously developed in many places.
One of the devices essential for practical application of such light transmission systems is a light switch usable between a light transmitter or receiver and a multitude of light transmission lines for switching therebetween or, that is useable, between a light transmission line and a plurality of light transmitters or receivers for switching therebetween. It is required that such a device be above all, compact in size, low in insertion loss, inexpensive and highly reliable.
Previously proposed are a number of forms of multichannel light switches which are usable to direct a light beam as desired through a single optical fiber into any one of a number of other optical fibers. In one form of such a light switch, four optical fibers are arranged in a rectangular case, one fiber along each of its four parallel edges and another optical fiber, clad with magnetic material, is arranged in opposing relation to the set of four optical fibers in a manner such that it may be displaced under the attraction of an exterior magnet so as to be switched over from one to another of the four fibers. (See the article, "Optical Fiber Line Switch (II)", Katsuhiro Suzuki et al, in the Proceedings of the 1978 National Convention of the Institute of Electronics and Communications Engineers of Japan, Vol. 4, p. 4-113, March 1978).
This form of light switch, however, is disadvantageous in that it is liable to fail or break owing to the movements required of the optical fiber for switching operations and time-consuming adjusting work is required to set each of the optical fibers precisely in place.
In another form of multichannel light switch previously proposed, a plurality of optical fibers each with a light-focusing transmission body attached thereto are radially arranged on a plane.
Another optical fiber, again with a light-focusing transmission body attached thereto, is arranged on an axis extending through the center of the plane at right angles thereto. For switching the light path between the central optical fiber and the radially arranged ones, a plane mirror is disposed in the central region at an angle of inclination of 45.degree. to the plane and is rotatable about the axis referred to above. (See the article, "Motor-driven Rotary Mirror Type Multichannel Light Switch", Ikuo Mito et al, in the Proceedings of the 1978 National Convention of Electronics and Communications Engineers of Japan, Vol. 4, p. 4-117, March 1978.) This form has disadvantages because it involves alignment difficulties in optimum-positioning optical fibers, and it is costly, because of the number of light-focusing transmission bodies employed.